Vibratory Penetration of Soils

1967 ◽  
Vol 89 (4) ◽  
pp. 759-765 ◽  
Author(s):  
M. Senator
Keyword(s):  
Coulomb Friction ◽  
Approximate Expression ◽  
Analog Computer ◽  
Approximate Theory ◽  
Harmonic Force ◽  
Force Amplitude ◽  
Limiting Case ◽  
Important Design ◽  
Small Excess ◽  
Good Agreement

An approximate expression is found for the penetration rate of a flexible penetrator, modeled as two masses joined by an elastic member with damping, with applied bias and harmonic forces. Modified Coulomb friction is used to characterize soil resistance. The approximate theory is compared with analog computer measurements and with an exact theory (developed for the limiting case of zero front mass and internal damping) and is found to give good agreement in lite range of small excess harmonic force amplitude. A comparison with a rigid penetrator is also made, and the flexible penetrator is shown to have the important design advantage of smaller weight or smaller applied harmonic force for equal penetration rates.

scholarly journals CuO–Water Nanofluid Magnetohydrodynamic Natural Convection inside a Sinusoidal Annulus in Presence of Melting Heat Transfer

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
M. Sheikholeslami ◽  
R. Ellahi ◽  
C. Fetecau
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Natural Convection ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Melting Heat ◽  
Melting Heat Transfer ◽  
Limiting Case ◽  
Good Agreement ◽  
Melting Parameter

Impact of nanofluid natural convection due to magnetic field in existence of melting heat transfer is simulated using CVFEM in this research. KKL model is taken into account to obtain properties of CuO–H2O nanofluid. Roles of melting parameter (δ), CuO–H2O volume fraction (ϕ), Hartmann number (Ha), and Rayleigh (Ra) number are depicted in outputs. Results depict that temperature gradient improves with rise of Rayleigh number and melting parameter. Nusselt number detracts with rise of Ha. At the end, a comparison as a limiting case of the considered problem with the existing studies is made and found in good agreement.

A Stochastic Theory for Nonlinear Ship Rolling in irregular Seas

1982 ◽  
Vol 26 (04) ◽  
pp. 229-245 ◽  
Author(s):  
J. B. Roberts
Keyword(s):  
Markov Processes ◽  
Digital Simulation ◽  
Stochastic Theory ◽  
Simple Expression ◽  
Roll Angle ◽  
Rolling Motion ◽  
Approximate Theory ◽  
Averaging Techniques ◽  
Good Agreement ◽  
Ship Rolling

By a combination of averaging techniques with the theory of Markov processes, an approximate theory is developed for the rolling motion of a ship in beam waves. A simple expression is obtained for the distribution of the roll angle, and is tested by a comparison with a set of digital simulation estimates due to Dalzell. Good agreement is obtained over a realistic range of damping values.

scholarly journals Vibroimpact Mobile Robot

2021 ◽  
Vol 17 (4) ◽  
pp. 429-436
Author(s):  
A. P. Ivanov ◽  
Keyword(s):  
Simple Model ◽  
Mobile Robot ◽  
Periodic Motion ◽  
Horizontal Plane ◽  
Coulomb Friction ◽  
Average Velocity ◽  
Moving Mass ◽  
Harmonic Force ◽  
Maximal Average ◽  
The Right

A simple model of a capsule robot is studied. The device moves upon a rough horizontal plane and consists of a capsule with an embedded motor and an internal moving mass. The motor generates a harmonic force acting on the bodies. Capsule propulsion is achieved by collisions of the inner body with the right wall of the shell. There is Coulomb friction between the capsule and the support, it prevents a possibility of reversal motion. A periodic motion is constructed such that the robot gains the maximal average velocity.

Design of a Disturbance Accommodating Adaptive Control System and Its Application to a DC-Servo Motor System With Coulomb Friction

1988 ◽  
Vol 110 (4) ◽  
pp. 343-349 ◽  
Author(s):  
P. N. Nikiforuk ◽  
K. Tamura
Keyword(s):  
Adaptive Control ◽  
Control System ◽  
Coulomb Friction ◽  
Motor System ◽  
Position Control ◽  
Adaptive Controller ◽  
Analog Computer ◽  
Adaptive Control System ◽  
Servo Motor ◽  
Analytical Functions

This paper discusses the design of a model reference type of adaptive control system for a linear unknown plant with system and observation disturbances. The disturbances are assumed to be approximately expressed by step, sinusoidal, and other analytical functions. The design of a controller, called a disturbance accommodating adaptive controller (DAAC), which eliminates the effect of these disturbances at the plant output, is described. Two types of bias DAAC are given as examples and are applied to the adaptive control of a DC-servo motor system. The plant (the DC-servo system) consists of two unknown loads connected through an electrical clutch and Coulomb friction. The effect of the friction on the plant is considered as an unknown bias disturbance and the DAAC is implemented on an analog computer. Experimental results for the position control of the DAAC system are given.

Pressurized Cylindrical Shell With a Rigid Circular Inclusion

1978 ◽  
Vol 100 (2) ◽  
pp. 158-163 ◽  
Author(s):  
D. H. Bonde ◽  
K. P. Rao
Keyword(s):  
Differential Equation ◽  
Cylindrical Shell ◽  
Shallow Shell ◽  
Circular Inclusion ◽  
Hankel Functions ◽  
Curvature Parameter ◽  
Shell Equations ◽  
Limiting Case ◽  
Rigid Circular Inclusion ◽  
Good Agreement

The effect of a rigid circular inclusion on stresses in a cylindrical shell subjected to internal pressure has been studied. The two linear shallow shell equations governing the behavior of a cylindrical shell are converted into a single differential equation involving a curvature parameter and a potential function in nondimensionalized form. The solution in terms of Hankel functions is used to find membrane and bending stressses. Boundary conditions at the inclusion shell junction are expressed in a simple form involving the in-plane strains and change of curvature. Good agreement has been obtained for the limiting case of a flat plate. The shell results are plotted in nondimensional form for ready use.

scholarly journals Linear and nonlinear responses to harmonic force in rotating flow

2016 ◽  
Vol 796 ◽  
pp. 306-317 ◽  
Author(s):  
Xing Wei
Keyword(s):  
Resonant Frequency ◽  
Nonlinear Regime ◽  
Rotating Flow ◽  
Force Frequency ◽  
Linear Regime ◽  
Harmonic Force ◽  
Force Amplitude ◽  
Ekman Number ◽  
Suppression Effect ◽  
Linear And Nonlinear

For understanding the dissipation in a rotating flow when resonance occurs, we study the rotating flow driven by the harmonic force in a periodic box. Both the linear and nonlinear regimes are studied. The various parameters such as the force amplitude $a$, the force frequency ${\it\omega}$, the force wavenumber $k$ and the Ekman number $E$ are investigated. In the linear regime, the dissipation at the resonant frequency scales as $E^{-1}k^{-2}$, and it is much stronger than the dissipation at the non-resonant frequencies on large scales and at low Ekman numbers. In the nonlinear regime, at the resonant frequency the effective dissipation (dissipation normalised with the square of the force amplitude) is lower than in the linear regime and it decreases with increasing force amplitude. This nonlinear suppression effect is significant near the resonant frequency but negligible far away from the resonant frequency. Opposite to the linear regime, in the nonlinear regime at the resonant frequency the lower Ekman number leads to lower dissipation because of the stronger nonlinear effect. This work implies that the previous linear calculations overestimated the tidal dissipation, which is important for understanding the tides in stars and giant planets.

Vibration of a Rotating Asymmetric Shaft Supported in Asymmetric Bearings

1968 ◽  
Vol 10 (3) ◽  
pp. 252-261 ◽  
Author(s):  
H. F. Black ◽  
A. J. McTernan
Keyword(s):  
Natural Frequencies ◽  
Equations Of Motion ◽  
Forced Vibrations ◽  
Variation Method ◽  
Approximate Theory ◽  
Cross Sectional ◽  
Mass Unbalance ◽  
The Mean ◽  
Theoretical Results ◽  
Good Agreement

The parametrically excited vibrations of this system with assumed small asymmetry of the shaft cross-section are discussed in terms of the motion of a symmetric shaft having the mean cross-sectional flexibility, and the equations of motion are solved by the approximate perturbation-variation method of Hsu. Both features yield a more lucid appreciation of the motions expected than previous treatments: in particular, simpler explicit expressions for unstable bounds are given and forced vibrations due to mass unbalance are discussed with greater facility. The practically important case of nearly coincident natural frequencies is examined. The theoretical results are compared with analogue computation: good agreement with the approximate theory is found even for quite large shaft asymmetry.

Designing and Harnessing the Metastable States of a Modular Metastructure for Programmable Mechanical Properties Adaptation

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
R. L. Harne ◽  
Z. Wu ◽  
K. W. Wang
Keyword(s):  
Mechanical Properties ◽  
Metastable States ◽  
System Level ◽  
Macroscopic System ◽  
Actin Networks ◽  
Module Design ◽  
Design Variables ◽  
Module Development ◽  
Important Design ◽  
Good Agreement

Recent studies on periodic metamaterial systems have shown that remarkable properties adaptivity and versatility are often the products of exploiting internal, coexisting metastable states. Motivated by this concept, this research develops and explores a local-global design framework wherein macroscopic system-level properties are sought according to a strategic periodic constituent composition and assembly. To this end and taking inspiration from recent insights in studies of multiphase composite materials and cytoskeletal actin networks, this study develops adaptable metastable modules that are assembled into modular metastructures, such that the latter are invested with synergistic features due to the strategic module development and integration. Using this approach, it is seen that modularity creates an accessible pathway to exploit metastable states for programmable metastructure adaptivity, including a near-continuous variation of mechanical properties or stable topologies and adjustable hysteresis. A model is developed to understand the source of the synergistic characteristics, and theoretical findings are found to be in good agreement with experimental results. Important design-based questions are raised regarding the modular metastructure concept, and a genetic algorithm (GA) routine is developed to elucidate the sensitivities of the properties variation with respect to the statistics amongst assembled module design variables. To obtain target multifunctionality and adaptivity, the routine discovers that particular degrees and types of modular heterogeneity are required. Future realizations of modular metastructures are discussed to illustrate the extensibility of the design concept and broad application base.

Modeling of a Finger-Follower Cam System With Verification in Contact Forces

1996 ◽  
Vol 118 (1) ◽  
pp. 132-137 ◽  
Author(s):  
Wensyang Hsu ◽  
A. P. Pisano
Keyword(s):  
Coulomb Friction ◽  
Constraint Equation ◽  
Contact Forces ◽  
Dynamic Responses ◽  
Distributed Parameter ◽  
Contact Points ◽  
Frictional Forces ◽  
Contact Position ◽  
Force Data ◽  
Good Agreement

A lumped/distributed-parameter dynamic model is developed to investigate the dynamic responses of a finger-follower cam system by considering a hydraulic lash adjuster with an oscillating pivot, and frictional forces between sliding surfaces. The measured force data at low speed are employed to derive an algorithm to determine the dynamic Coulomb friction coefficients at contact points. The contact position between the cam and the follower with moving pivot is determined by a constraint equation method. A hydraulic lash adjuster acting as the pivot of the follower is also modeled with the effects of oil compressibility and oil refill mechanism. Simulated contact forces at three different speeds are shown to have good agreement with experimental data. The separation between the hydraulic lash adjuster and the follower is predicted at a camshaft speed of 2535 rpm, and experiment indicates at 2520 rpm.

Some Problems of Press Forging Lead and Aluminum

1960 ◽  
Vol 82 (3) ◽  
pp. 246-252 ◽  
Author(s):  
A. G. MacDonald ◽  
S. Kobayashi ◽  
E. G. Thomsen
Keyword(s):  
Work Hardening ◽  
Room Temperature ◽  
Pure Aluminum ◽  
The Body ◽  
Approximate Theory ◽  
Substantial Agreement ◽  
Strain Rate Effects ◽  
Rate Effects ◽  
Local Pressures ◽  
Good Agreement

Several press forgings were made and it was found that the experimental mean forging pressures were in substantial agreement with values predicted by theoretical solutions based on an approximate theory. The forging processes were axial symmetric forging of disks between flat dies and forging in closed dies with several edge effects, such as overhanging flash, with and without flash-edge restriction. The materials were commerically pure aluminum and lead and were chosen because of their respective work-hardening and strain-rate effects at room temperature. It was found further that the local pressures measured in the forging were in good agreement with the theory, but that some local plastic flow tends to equalize the pressure in the body of the forging.

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